Other Comprehensive Income (Loss) (Component Of Accumulated Other Comprehensive Income (Loss)) (Details) - USD ($) $ in Thousands	3 Months Ended
	Mar. 31, 2019	Mar. 31, 2018	Dec. 31, 2018	Dec. 31, 2017
Accumulated Other Comprehensive Income (Loss) [Line Items]
Share-based Compensation Arrangement by Share-based Payment Award, Options, Vested and Expected to Vest, Outstanding, Number	165,279
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, before Tax		$ 2,600
Other comprehensive loss before reclassifications	$ 14,335	(23,410)
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), Reclassification, after Tax		0
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets				$ (995)
Other Comprehensive (Income) Loss, Defined Benefit Plan, after Reclassification Adjustment, after Tax	0	0
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), after Reclassification and Tax	(206)	0
Other Comprehensive Income (Loss), Reclassification Adjustment from AOCI for Sale of Securities, Net of Tax	0	2,024
Reclassification from Accumulated Other Comprehensive Income, Current Period, Net of Tax		2,024
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, after Tax		(21,386)
Other comprehensive income (loss)	14,335	(21,386)
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, before Reclassification Adjustments, after Tax	14,541	(23,410)
Other Comprehensive (Income) Loss, Defined Benefit Plan, before Reclassification Adjustment, after Tax	0	0
Other Comprehensive Income (Loss), Cash Flow Hedge, Gain (Loss), before Reclassification, after Tax	(206)	0
Changes in pension plan assets and benefit obligations, Net-of-tax amount	(29,672)	(26,701)	$ 29,672	23,526
AOCI, Cash Flow Hedge, Cumulative Gain (Loss), after Tax	(206)	0	0	0
Unrealized gains on available-for-sale securities, Net-of-tax amount	(5,575)	(25,940)	(20,116)	(2,928)
Total accumulated other comprehensive income (loss), Net-of-tax amount	(35,453)	$ (52,641)	$ (49,788)	(26,454)
Other Comprehensive (Income) Loss, Reclassification Adjustment from AOCI for Write-down of Securities, before Tax	0
Accumulated Other Comprehensive Income (loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets				(3,806)
Accumulated Other Comprehensive Income (loss) [Member] | Pension Plan [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets				(3,175)
Accumulated Other Comprehensive Income (loss) [Member] | Debt Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets				(631)
Accounting Standards Update 2016-01 [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other comprehensive income (loss)	14,335
Accounting Standards Update 2016-01 [Member] | Debt Securities [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Other Comprehensive Income (Loss), Securities, Available-for-sale, Adjustment, after Tax	$ 14,541
Accounting Standards Update 2016-01 [Member] | Accumulated Other Comprehensive Income (loss) [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
New Accounting Pronouncement or Change in Accounting Principle, Cumulative Effect of Change on Equity or Net Assets				(995)
Adjustments for New Accounting Pronouncement [Member]
Accumulated Other Comprehensive Income (Loss) [Line Items]
Changes in pension plan assets and benefit obligations, Net-of-tax amount				23,526
AOCI, Cash Flow Hedge, Cumulative Gain (Loss), after Tax				0
Unrealized gains on available-for-sale securities, Net-of-tax amount				(3,923)
Total accumulated other comprehensive income (loss), Net-of-tax amount				$ (27,449)